### Introduction

### Materials and Methods

- Pair 1: length of the V part on the right (LVR) and left (LVL) sides (Fig. 3)

- Pair 2: length of the posterior arch of C1 corresponding to the V3 segment on the right (LPR) and left (LPL) sides (Fig. 3); total length of the V part=length of the V part+length of the posterior arch of the atlas

- Pair 3: length of the H part on the right (LHR) and left (LHL) sides (Fig. 3)

- Pair 4: length of the E part on the right (LER) and left (LEL) sides

- Pair 5: length of the total V3 segment on the right (LTR) and left (LTL) sides. The total length of the V3 segment would be obtained by adding up the measured length of the V part, posterior arch of C1, H part, and E part.

- Pair 6: diameter of the V part on the right (DVR) and left (DVL) sides

- Pair 7: diameter of the H part on the right (DHR) and left (DHL) sides (Fig. 3)

- Pair 8: diameter of the E part on the right (DER) and left (DEL) sides (Fig. 3)

- Pair 9: average diameter (average diameter of the V, H, and E parts): on the right (DAR) and left (DAL) sides

### Results

*r*-value was weakly positive for the right (+0.003) and left (0.021) (Figs. 5, 6).

*r*-value was 0.911, which indicates strongly positive correlation. The

*p*-value in the correlation analysis was <0.001, which represents a significant correlation between AR and AL (Fig. 7). The correlation between the total length (LTR and LTL) and average diameter (DAR and DAL) of the V3 segment of the VA was also analyzed; however, no correlation was observed.

### Discussion

*r*-value was 0.911, and the

*p*-value of the correlation was <0.001, representing a significant correlation between AR and AL (Fig. 7). This may mean that the distribution of the blood supply to the brain is dependent on the angle formed between the V and H part on the right and left sides. However, a limitation of this study was that the analysis results were based on cadavers, and there might be a slight change in morphometric values compared with living individuals.

### Conclusions

First comprehensive cadaveric study of V3 segment of vertebral artery in South Indian population, measuring length, diameter, and angle of all three parts.

Left-sided vertebral artery longer than right (mean total length: 70.35 mm vs. 66.81 mm); mean diameters ranged 4.95–5.70 mm.

Strong positive correlation between right and left side angles (80.8° and 78.5°, respectively), suggesting dependency for balanced blood supply.

Morphometric data provides valuable reference for spine surgeons performing procedures in the atlantoaxial region.